Immunization is impaired in immunosuppressed individuals. This study demonstrated a dramatic impact of routine post-transplant immunosuppression on seroprotection after pH1N1 vaccination leaving approximately 2/3 without seroprotection. Importantly, 11.9% of vaccinated patients demonstrated new anti-HLA antibodies post vaccination. The authors inform future research into how to improve seroprotection without adversely affecting HLA antibody formation.